The present invention relates generally to nuclear reactors, and more particularly to mitigating acoustic loads in a nuclear reactor.
In boiling water nuclear reactor (BWR), reactor coolant flows through a series of plenums starting with a lower core plenum, the nuclear core itself and an upper core plenum, each lying in communication with one another. The upper core plenum lies below a shroud head which has a series of standpipes that lead steam/water to a series of separators where the two-phase mixture of steam and water is separated. The separated water flows downwardly in an annulus about the core shroud for recirculation. The separated steam flows upwardly of the reactor through a steam dryer for flow outside of the reactor vessel to drive a turbine for generating power.
In BWR's, this flowing mixture of vapor and liquid must be separated efficiently to provide the dry steam required for steam turbine generators. Typical reactor designs employ primary separators, each of which includes a standpipe connected to the upper core shroud and which standpipe is topped with a helical flow diverter to create a swirl flow into an enlarged separation barrel section. The resultant radial acceleration field causes the higher density liquid to move outward and flow as a film on the separation barrel. Radial pick-off rings are provided at one or more axial positions along the barrel to intercept the liquid film flow and separate it from the interior vapor flow. Discharge passages direct the separated water to a water pool which partially submerges the primary separators.
One of the sources of loading that has destroyed or damaged equipment is acoustic resonance of the fluid inside a standoff pipe, such as a safety relief valve. The safety relieve valve, or valves, with steam flow past their entrances, and the acoustic resonance which naturally occurs, causes acoustic pressures to travel upstream, causing damage to devices, for example, the steam dryers.
Previous attempts to reduce damage to devices such as steam dryers have included predicting or estimating the loading on the steam dryer using Finite Element Analysis (FEA), and computing the stress on the dryer, and modifying the dryer to decrease the computed stresses.
Another attempt to reduce the damage to equipment such as steam dryers has included a Helmholtz resonator provided on the relief valves. However, the Helmholtz resonator is a large cantilevered bottle-shaped device which is difficult to support in the environment of a nuclear power generating station.